This invention relates to a material for a light-emitting device which can convert electric energy to light, and to a light-emitting device which can suitably be utilized in the field of display device, display, back light, electrophotography, light source for illumination, light source for recording, light source for exposure, light source for readout, mark, billboard, interior decoration, optical communication and the like. In addition, it relates to an iridium complex showing a strong emission in a blue region.
At the present time, development and study on various display devices are aggresively driven. In particular, organic electric field light-emitting (EL) can obtain highly bright luminescence at a low voltage and accordingly, is drawing attention as a promising display device. For example, a light-emitting device comprising an organic thin film formed by depositing an organic compound is known (Applied Physics Letters, Vol. 51, page 913 (1987). The light-emitting device described in this publication has a laminate structure wherein a tris(8-hydroxyquinolinato)aluminum complex (Alq) is used as an electron transporting material and is layered on a hole transporting material (an amine compound), and is greatly improved in the luminescence properties due to the structure as compared with conventional single-layer devices.
In recent years, it has actively been investigated to apply organic EL devices to color display or white light source. However, in order to develop high performance color display and white light source, it is necessary to improve properties of each of blue light-emitting devices, green light-emitting devices and red light-emitting devices.
As a means for improving the properties of light-emitting devices, a green light-emitting device utilizing luminescence emitted from an ortho-metalated iridium complex (Ir(ppy)3: Tris-Ortho-Metalated Complex of Iridium(III) with 2-Phenylpyridine) has been reported (Applied Physics Letters 75, 4 (1999)). However, since Ir(ppy)3 emits only green light, it can be applied to only a limited scope of display. Thus, development of devices capable of emitting other color light (blue or red light) with a high efficiency have been required.
The present invention provides a light-emitting device with a high efficiency, and provides a novel metal complex capable of actualizing the device.
The above-described subjects of the invention can be solved by the following:
(1) A light-emitting device comprising:
a pair of electrodes; and
organic compound layers comprising a light-emitting layer provided in between the electrodes,
wherein at least one of the organic compound layers comprises a compound having a transition metal atom-phosphorus atom bond.
(2) The light-emitting device set forth in (1) above, wherein the compound having a transition metal atom-phosphorus atom bond is represented by the following formula (2): 
xe2x80x83wherein R21 represents a hydrogen atom or a substituent, L21 represents a ligand, X21 represents a counter ion, n21 represents 2 or 3, n22 represents an integer of 1 to 8, n23 represents an integer of 0 to 8, n24 represents an integer of 0 to 6, and, when n21, n22, n23 or n24 represents a plural number, R21 groups, (R21)n21xe2x80x94P ligands, L21 ligands or X21 ions are each the same or different.
(3) The light-emitting device set forth in (1) above, wherein the compound having a transition metal atom-phosphorus atom bond is a compound having a maximum emitted wavelength, xcexmax, in a range of 350 nm to 550 nm.
(4) The light-emitting device set forth in (1) above, wherein the layer comprising the compound having a transition metal atom-phosphorus atom bond is a layer formed by a coating process.
(5) The light-emitting device set forth in (1) above, wherein the compound having a transition metal atom-phosphorus atom bond is represented by the following formula (4): 
xe2x80x83wherein R41, R42, R43, R44 and R45 each independently represent a substituent, L41 represents a ligand, X41 represents a counter anion, m41 and m42 each independently represent an integer of 0 to 4, and n41 represents 0 or 1.
(6) The light-emitting device set forth in (1) above, wherein the compound having a transition metal atom-phosphorus atom bond is represented by the following formula (5): 
xe2x80x83wherein R51, R52, R53, R54, R55 and R56each independently represent a substituent, Z51 represents a linkage group, X51 represents a counter anion, and m51 and m52 each independently represent an integer of 0 to 4.
(7) The light-emitting device set forth in (1) above, wherein the compound having a transition metal atom-phosphorus atom bond is represented by the following formula (6): 
xe2x80x83wherein R61, R62, R63, R64 and R65 each independently represent a substituent, Z61 represents a linkage group, and m61 and m62 each independently represent an integer of 0 to 4.
(8) The light-emitting device set forth in (5) above, wherein L41 represents a halogen atom or a cyano group.
(9) The light-emitting device set forth in (6) above, wherein Z51 represents an alkylene group or an arylene group.
(10) The light-emitting device set forth in (7) above, wherein Z61 represents an alkylene group or an arylene group.
(11) The light-emitting device set forth in (5) above, wherein the compound represented by the formula (4) has a maximum emitted wavelength, xcexmax, in a range of 350 nm to 550 nm.
(12) The light-emitting device set forth in (6) above, wherein the compound represented by the formula (5) has a maximum emitted wavelength, xcexmax, in a range of 350 nm to 550 nm.
(13) The light-emitting device set forth in (7) above, wherein the compound represented by the formula (6) has a maximum emitted wavelength, xcexmax, in a range of 350 nm to 550 nm.
(14) The light-emitting device set forth in (5) above, wherein the layer comprising the compound represented by the formula (4) is a layer formed by a coating process.
(15) The light-emitting device set forth in (6) above, wherein the layer comprising the compound represented by the formula (5) is a layer formed by a coating process.
(16) The light-emitting device set forth in (7) above, wherein the layer comprising the compound represented by the formula (6) is a layer formed by a coating process.
(17) A compound represented by the following formula (4): 
xe2x80x83wherein R41, R42, R43, R44 and R45 each independently represent a substituent, L41 represents a ligand, X41 represents a counter anion, m41 and m42 each independently represent an integer of 0 to 4, and n41 represents 0 or 1.
(18) A compound represented by the following formula (5): 
xe2x80x83wherein R51, R52, R53, R54, R55 and R56 each independently represent a substituent, Z51 represents a linkage group, X51 represents a counter anion, and m51 and m52 each independently represent an integer of 0 to 4.
(19) A compound represented by the following formula (6): 
xe2x80x83wherein R61, R62, R63, R64 and R65 each independently represent a substituent, Z61 represents a linkage group, and m61 and m62 each independently represent an integer of 0 to 4.
(20) The light-emitting device set forth in (1) above, wherein the transition metal atom is an atom selected from the group consisting ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium and platinum.
(21) The light-emitting device set forth in (1) above, wherein the phosphorus atom constitutes a part of phosphorus ligand.
(22) The light-emitting device set forth in (21) above, wherein the phosphorus ligand is selected from the group consisting of an alkylphosphine and derivatives thereof, an arylphosphine and derivatives thereof, heteroarylphosphine and derivatives thereof, an alkoxyphosphine and derivatives thereof, an aryloxyphosphine and derivatives thereof, a heteroaryloxyaminophosphine and derivatives thereof, a phosphinine (phosphabenzene) and derivatives thereof, and aminophosphine and derivatives thereof.
(23) The light-emitting device set forth in (1) above, wherein x value on the CIE chromaticity diagram of the emitting is 0.22 or less, and y value on the CIE chromaticity diagram of the emitting is 0.53 or less.
(24) The light-emitting device set forth in (1) above, which emits spectrum having a half band width of 1 nm to 100 nm.
(25) The light-emitting device set forth in (2) above, wherein the valence number of iridium is trivalent.
(26) The light-emitting device set forth in (1) above, wherein the content of the compound having a transition metal atom-phosphorus atom bond in the light-emitting layer is from 0.1% to 100% by weight based on the total composition of the light-emitting layer.
(27) The light-emitting device set forth in (1) above, wherein the content of the compound having a transition metal atom-phosphorus atom bond in the light-emitting layer is from 1% to 50% by weight based on the total composition of the light-emitting layer.
(28) The light-emitting device set forth in (1) above, wherein the content of the compound having a transition metal atom-phosphorus atom bond in the light-emitting layer is from 5% to 30% by weight based on the total composition of the light-emitting layer.